In our physical world, we have two fundamental components. There is matter and then there is how matter interacts. Those interactions are forces that occur between matter particles and can be broken into microscopic observations.
Electroweak theory is a description of particle physics that fits within the Standard Model. It is a unified description of half of the known fundamental interactions that occur in nature, specifically nuclear weak interactions and electromagnetism. At low energies, these forces appear to be very different. In the electroweak theory, however, they are modeled as being two different aspects of the same force.
When merged together, they become a single electroweak force.
he Fundamental Force of Electromagnetism
Nearly every physical phenomenon that exists in our universe is a result of electromagnetism. That includes sound, light, soil, and color. As intermolecular forces form between atoms and molecules, the electromagnetic force is manifested. Electrons are bound to atomic nuclei, governing the processes of chemistry that arise as they interact with their neighboring atoms.
Electromagnetism is also responsible for explaining how those particles are able to carry momentum through their movement. The forces “push” or “pull” on material objects because of the processes of chemistry.
Imagine that you are holding two powerful magnets, one in each hand. They will attract one another when the poles are aligned and you can feel the force of them coming together. If the poles are opposed, however, you will feel resistance as you attempt to bring the two magnets together. That force strengthens the closer you bring the magnets together.
This is similar to the effect that is seen on the microscopic level and why its energy can be seen in the form of light from very great distances.
The Fundamental Force of the Nuclear Weak Force
The nuclear weak force is involved in radioactivity. It is what causes the atomic nuclei to begin decaying. Unlike electromagnetism, the weak force only works on a microscopic scale.
There are a number of reasons why the weak interaction is quite unique.
1. It is the only interaction in the Standard Model that is known to be able to change one type of quark into another type of quark. This is referred to as changing the quark’s “flavor.” All 6 quark types can be modified by weak interaction: strange, charm, top, bottom, up, and down.
2. It is the only known interaction that violates parity symmetry and charge-parity symmetry. The various discoveries that have led to this conclusion have been the basis of several Nobel Prizes.
3. It is mediated by force carrier particles that have a significant mass, which is unusual for a Standard Model with the Higgs mechanism.
The weak interaction does not produce bound states or involve binding energy, which electromagnetism does at the atomic level. There are, however, two types of interaction, referred to as “vertices,” that are possible and it is based on the boson involved.
Why Do the Two Forces Appear to Be Different?
Electroweak theory brings together electromagnetism and weak interaction, even though they appear to be very different from one another.
On a superficial level, electromagnetic forces extend for great distances. This is seen because the light of a star can bridge the gap between galaxies. At the same time, the nuclear weak force acts on distances that are very small, no greater than the distance of a single atomic nucleus. When the strength of these two forces are compared, the nuclear weak force is about 10 million times weaker than the electromagnetic force.
Despite their initial differences in aesthetics, both forces act upon the same basic structure thanks to the existence of force carriers. These carriers are charged W-particles and neutral Z-particles that are called “bosons.”
These bosons have a spin of either 1 or 0. W-bosons are named after the nuclear weak force because that is their responsibility in the electroweak theory. These bosons are formed through Beta decay and it is believed that W-bosons can break down radioactive elements to stimulate Beta decay, creating a self-sustaining model for their creation.
Z-bosons, on the other hand, are predicted to decay into fermions and their antiparticles.
At the same time, the W-bosons are carrying charges under the electromagnetic force. That is why the electroweak force is suggested and allows through the theory for the two to mix together.
Weak interaction creates charged-current interaction on the W-boson, which is how Beta Decay is formed. Neutral-current interaction is formed through mediation with the Z-boson.
The Unifying Forces of the Electroweak Theory
Two additional force carriers are included with the electroweak theory. There is an antiparticle to the W-boson and another uncharged particle that mix at low energy levels. As these four forces travel together, they can mix up together and even evolve into each other. Massless photons are possible and so are Z-bosons.
At high energy levels and when all these particles are moving at speeds that are close to the speed of light, their interactions become the basis of the electroweak theory.
Yet this also provides three particles that have mass at varying levels and one particle that has zero mass. To explain this issue, the Standard Model incorporated the existence of the Higgs field, which has been confirmed via experimental investigation. Ongoing work on the Higgs field and Higgs boson may help to create a more unified theory, but also confirms the findings made by the electroweak theory.
It has also been discovered that the electroweak theory can be renormalized.
Electroweak Theory and Symmetry Violation
For many generations, the laws of nature were thought to remain the same when reflected. An experiment, when viewed through a mirror, could produce identical mirror-reflected results. This was known as parity conservation. In the 1950s, weak interactions were determined to violate this law.
Particles in the electroweak theory, whether they are right-handed or left-handed in their reflection, will exhibit the same direction of momentum. The spin of the particle remains consistent with the principles proposed by parity conservation, however, and that creates a lack of reflective symmetry between the two states.
In some ways, the more we learn about the universe as we pursue a unified theory of everything, we discover that we know very little. More questions develop than answers we can find. Yet in the grand scheme of things, the Standard Model and its electroweak theory provide a theory of “almost everything.”
There is a certain beauty in particle physics that seems like evidence of a cohesive design to the universe. Maybe that design was created by a supernatural being. Maybe it was created through the laws of nature. What we do know is that as we continue to learn more about these fundamental interactions, we continue to discover more about ourselves at the same time.